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Change-Wheel Mystery

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Change-Wheel Mystery

Home › Forums › Manual machine tools › Change-Wheel Mystery

Viewing 6 posts - 1 through 6 (of 6 total)
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  • 5 January 2015 at 18:01 #174859
    Michael Gilligan
    Participant
      @michaelgilligan61133

      The  little Jason lathe came with only the auto-traverse gearing

      • Driver on headstock spindle: 32
      • Compound Gear: 32/16
      • Compound Gear: 56/20
      • Driven Gear on leadscrew: 64
      • Leacdscrew tpi: 16

      This gives a traverse equivalent to 179.2 tpi.

      … Fair enough, I suppose; but why choose those counts?

      Now the plot thickens: it appears that the Cowells ME90 comes with the same numbers, except that they are all seperate gears, and it [now] has a metric leadscrew.

      Brian Perris was the original designer of both machines, so perhaps it just reflects his preference [or the gears he had in-stock at the time] … but I would be grateful if anyone could provide a logical reason

      MichaelG.

      Edited By Michael Gilligan on 05/01/2015 18:04:33

      Edited By Michael Gilligan on 05/01/2015 18:06:27

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      5 January 2015 at 18:01 #12403
      Michael Gilligan
      Participant
        @michaelgilligan61133

        strange choice for auto-traverse …

        5 January 2015 at 18:56 #174864
        Bazyle
        Participant
          @bazyle

          They are all multiples of 8 (20 being a compromise for 40). Common change gear sets are either multiples of 5 or multiples of 8 with a few strays thown in. I suspect the full set for the ME90 filled in the gaps.

          A cunning salesman would have arranged that the supplied gears didn't quite give the most wanted threads pushing the user into an early purchase of a few more.

          5 January 2015 at 19:09 #174865
          Michael Gilligan
          Participant
            @michaelgilligan61133
            Posted by Bazyle on 05/01/2015 18:56:34:

            … (20 being a compromise for 40) …

            .

            Aha !! … That's the 'logic' I had missed

            … I kept focussing on the factor of 5

            Thanks

            MichaelG.

            5 January 2015 at 20:54 #174876
            Neil Wyatt
            Moderator
              @neilwyatt

              Brian Perris was apparently measured at exactly 5' 10.551" during a visit to the NPL. I think it's probably his little joke

              Seriously, why 56 rather than the more usual 57 (oft needed for 19tpi)?

              Neil

              5 January 2015 at 21:13 #174879
              duncan webster 1
              Participant
                @duncanwebster1

                Screwcutting 19tpi on a cowells sounds a bit optimistic to me, the chip width is 40 thou. Mie wouldn't do that, at the very least the chuck would not grip (perhaps I need another chuck, it's a lever scroll thing)

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